Stabilized melt-processable ethylene/chlorotrifluoroethylene copolymer compositions

ABSTRACT

ABOUT EQUIMOLAR ETHYLENE/CHLOROTRIFLUOROETHYLENE COPOLYMER COMPOSITIONS ARE STABILIZED AGAINST THERMAL DEGRADIATION SO AS TO RENDER THEM MELT-PROCESSABLE BY INCORPORATING THEREIN A STABILIZING SYSTEM COMPRISING (A) A PHOSPHITE OF AN ORGANIC POLYHYDRIC PHENOL; (B) A SALT OF A CARBOXYLIC ACID AND A METAL OF GROUP II OF THE PERIODIC TABLE; (C) A THIO DIPROPIONIC ACID ESTER OR ALKALI METAL SALT.

United States Patent O 3,745,145 STABHJIZED MELT-PROCESSABLE ETHYLENE/CHLOROTRIFLUOROETHYLENE COPOLYMER COMPOSITIONS Ghazi Khattab,Parsippany, and Alfred Stoloif, Livingston, N.J., assignors to AlliedChemical Corporation, New

York, N.Y. No Drawing. Filed Mar. 16, 1971, Ser. No. 124,913 lint. Cl.C08f 45/62 U.S. Cl. 260-45.75 XA 16 Claims ABSTRACT OF THE DISCLOSUREAbout equimolar ethylene/chlorotrifluoroethylene copolymer compositionsare stabilized against thermal degradation so as to render themmelt-processable by incorporating therein a stabilizing systemcomprising (a) a phosphite of an organic polyhydric phenol; (b) a saltof a carboxylic acid and a metal of Group II of the Periodic Table; (c)a thio dipropionic acid ester or alkali metal salt.

BACKGROUND OF THE INVENTION This invention relates to stabilized,melt-processable ethylene/chlorotrifiuoroethylene copolymercompositions, especially of about equimolarethylene/chlorotrifluoroethylene copolymers, and more particularly, to aprocess for stabilizing about equimolar ethylene/chlorotrifluoroethylenecopolymers against degradation during fabrication and use at elevatedtemperatures.

About equimolar ethylene/chlorotrifiuoroethylene copolymers exhibitoutstanding mechanical, electrical and chemical properties at hightemperatures. For example, about equimolarethylene/chlorotrifluoroethylene copolymers resist attack of mostorganic solvents at ambient as Well as elevated temperatures, being onlyslightly soluble at 1-00-1'50 C. in2,S-dichlorobenzotrifluoride/benzonitrile or O-dichlorobenzene mixturesof :90 to 50:50 volume ratio. They are insoluble in bases and acids,ineluding fuming nitric acid. These copolymers also possess high tensilestrength and have melting points above about 220 C. and as high as about260 C., which melting points are higher than those of the homopolymersof either ethylene (as high as 130 C.) or chlorotrifluoroethylene (ashigh as 215 0.). About equimolar ethylene/ chlorotrifluoroethylenecopolymers also have outstanding electrical properties. For all of theseadvantageous properties, they are eminently suitable for making usefularticles, such as valves, gaskets, pipes, wire insulation, sheets orfilms for use in applications where their excellent mechanical,electrical and chemical properties can be used to advantage. Up to now,however, such ethylene/chlorotrifluoroethylene copolymer compositionshave not found significant commercial use because they are inherentlythermally unstable so that they cannot readily be fabricated byconventional melt-processing operations, as extrusion or injectionmolding. About equimolar ethylene/ chlorotrifiuoroethylene homopolymers,due to their high melting points in excess of about 220 C., require meltfabrication temperatures of above about 250 0, usually within the rangeof between about 260 C. to 320 C. At these high temperatures rapiddegradation of the polymer occurs resulting in discoloration and loss ofchemical, mechanical and electrical properties. In particular,degradation of these properties occurs during extrusion and injectionmolding operations.

Stabilizers which have been proposed to retard thermal degradation oftrifluorochloroethylene polymers, such as zinc oxide, hydroquinone,chloranil, or mixtures thereof do not provide adequate stabilization ofabout equimolar 3,745,145 Patented July 10, 1973 iceethylene/chlorotrifluoroethylene copolymers even when employed inamounts well above those in which such stabilizers are conventionallyemployed. Moreover, when zinc oxide is used in amount in excess of about1% by weight of the polymer, the product is rendered white and opaqueand has inferior mechanical and electrical properties. Use ofhydroquinone and/or chloranil in amount above about .5% by weight of thepolymer, either alone or in combination with zinc oxide, causesformation of bubbles and intense discoloration in the polymer.

Stabilizers commonly used to retard thermal degradation of polyethylene,such as butylated hydroxy toluene, 1,1,3tris(2-methy1-4-hydroxy-5-tert.butylphenyl)butane or4,4-n-butylidene-bis(6-tert.butyl-m-cresol) do not provide protectionagainst thermal degradation during melt processing ofethylene/chlorotrifluoroethylene copolymers, especially about equimolarethylene/chlorotrifiuoroethylene copolymers having melting points inexcess of about 220 C.

It is an object of the present invention to provide a process forimproving the thermal stability of ethylene/ chlorotrifluoroethylenecopolymers.

Another object of the invention is to provide meltprocessablecompositions comprising ethylene/chlorotri- :fluoroethylene copolymersand stabilizers therefor.

More specifically, it is an object of the present invention to provide aprocess for improving the thermal stability of about equimolarethylene/chlorotrifiuoroethylene copolymers, and to providemelt-proeessable compositions comprising about equimolarethylene/chlorotrifluoroethylene copolymers.

It is a further object of the present invention to providemelt-processable compositions comprising about equimolarethylene/chlorotrifluoroethylene which are also resistant to thermaldegradation on long term exposure to elevated temperatures.

Other objects and advantages will become apparent to those skilled inthe art from the following description and disclosure.

DESCRIPTION OF THE INVENTION 10% by weight of the polymer of a salt of amonocarboxylie acid having from about 6 to about 24 carbon atoms and amelt of Group II of the Periodic Table; and (c) 0.01 to 10% by weight ofthe polymer of an ester or alkali metal salt of thiodipropionie acid.

Although each individual component, or the combination of any twocomponents of the stabilizing mixture fails to effect satisfactorystabilization of ethylene/chlorotrifluoroethylene copolymers, thethree-component mixture surprisingly eifects excellent stabilization ofthe polymer against thermal degradation, not only during shorttermexposure to elevated temperatures, as encountered duringmelt-processing, but also in long-term exposure in use in hightemperature environments. Moreover, the stabilizing mixtures of thepresent invention do not adversely affect the physical and electricalproperties of these copolymers.

The ethylene/chlorotrifluoroethylene copolymers which may be stabilizedin accordance with the present invention are high molecular weight,normally solid, thermoplastic polymers containing between 40 and about60 mol percent of ethylene units in the molecule and having meltingpoints between about 200 and about 265 C. The stabilizing compositionsin accordance with the present invention are particularly advantageousfor use in about equimolar ethylene/chlorotrifluoroethylene copolymerscontaining between about 45 and about 5 5 mol percent of ethylene unitsand having melting points above about 220 C.

These copolymers may be prepared by processes well known to thoseskilled in the art, as described, for example, in Hanford U.S. Pat.2,392,378, which shows copolymerization of ethylene withchlorotrifluoroethylene in a stirred aqueous medium at superatmosphericpres sure using benzoyl peroxide as catalyst; in Nucleonics, September,1964, pp. 72-74, disclosing formation of a high melting (237 C.) 1:1alternant copolymer of ethylene and chlorotrifiuoroethylene preparedusing a radiation catalyst at 0 C.; or British Pat. 949,422, showingbulk copolymerization of ethylene with chlorotrifluoroethylene attemperatures between -80 to -|-50 C. using oxygen-activated alkyl boroncatalyst; or Ragazzini et al. U.S. Pats. 3,371,076 and 3,501,446,respectively relating to methods for makingethylene/chlorotrifiuoroethylene copolymers using oxygen-activatedboron-containing catalysts and to products obtained by that process.About equimolar ethylene/chlorotrifluoroethylene copolymers having highmelting point above 200 C. can also be prepared by batchwise bulkcopolymerization of the monomers of temperatures of about 0 C., saybetween about ---20 to +20 C., at superatmospheric pressure in anagitatorequipped pressure vessel by charging the vessel with liquidchlorotrifluoroethylene monomer and bubbling gaseous ethylene into thismonomer, using organic peroxide-type initiators, such as trichloroacetylperoxide and, if desired, adding small amounts of chain transfer agents,such as chloroform or heptane. The desired copolymer products isobtained as a dispersion in the monomer.

The organic polyhydric phenols used to obtain the transesterifiedreaction product used inthe polymer compositions of the presentinvention have the formula l @wclo M (RM:

wherein X is selected from the group consisting of oxygen, sulfur,alkylene, alicyclidene, arylidene and mixed alkylenearylidene andalkylene-alicyclidene groups, wherein the aliphatic or cycloaliphaticportion of the molecule may be straight chain or branched chain, havingfrom 1 to about 18 carbon atoms; wherein the R substituents, which maybe the same or different, are independently selected from the groupconsisting of hydrogen and alkyl, straight or branched chain, havingfrom 1 to about 18 carbon atoms; and wherein m and n are integers from 1to 5, and o and p are integers from 0 to 4, with the proviso that thesums of m+0, and n+p may not exceed 5. The OH groups preferably are inortho and/or para position to X.

Transesterified reaction products of organic polyhydric phenols andorganic phosphite triesters suitable for use in the presently claimedinvention are described, for example, in U.S. Pats. 3,244,650 and3,255,136, both issued to Hecker et al. The description of thesetransesterification products given herein is principally based on thatgiven in Hecker et al.s U.S. Pat. 3,244,650.

As described in U.S. Pat. 3,244,650, suitable polyhydric phenols includeorcinol, catechol, resorcinol, p-octyl resorcinol, p-dodecyl resorcinol,p-octadecyl catechol, p-isooctyl-phloroglucinol, pyrogallol, hexahydroxybenzene, pisohexyl-catechol, 2,6-ditertiary butyl resorcinol,2,6-diisopropyl phloroglucinol, methylenebis-(2,6-ditertiarybutyl-m-cresol), methylenebis(2,6-ditertiary butyl phenol), 2,2-bis(4-hydroxy phenyl) propane, methylenebis(p-cres0l),4,4-thiobis(3-methy1-6-tertiary butyl phenol), 2,2'-oxobis- (4-dodecylphenol), 2,2-thiobis(4-methyl-6-tertiary butyl phenol), 2,6-diisooctylresorcinol, 4,4-n-butylidenebis-(2, 4-butyLS-methylphenol), 4,4benzylidenebis(2-t-butyl)-5- methylphenol2,2-methylenebis-(4-methyl-6-1'-methylcyclohexylphenoyl), 4,4cyclohexylidenebis-(Z-t-butylphenol), 2,6-bis (2'-hydroxy-3'-t-butyl-5-methylbenzyl) -4- methylphenol, 4-octyl pyrogallol, and3,5-ditertiary butyl catechol.

Especially preferred polyhydric phenols are 4,4'-n-butylidene-bis-(G-tert-butyl-m-cresol) and 1,1,3-tris(2-methyl-4-hydroxy-S-tert-butylphenyl)butane.

Organic phosphites suitable for making the transesterified reactionproducts of organic polyhydric phenol and organic phosphite triesterused in the stabilizer compositions of the present invention are alsodescribed in U.S. Pat. 3,244,650. They can be any organic phosphitehaving the formula: (Ra) P wherein a is selected from the groupconsisting of oxygen, sulfur and mixtures thereof, and R is selectedfrom the group consisting of aryl, alkyl, cycloalkyl, aryl-alkyl,al-kyl-aryl and combinations thereof. The term organic phosphitetriester, as used herein, includes oxo, thio and mixed oXo-thiophosphites. For reasons of availability, the phosphite will not usuallyhave more than 60 carbon atoms. Exemplary suitable phosphites includethose listed in U.S.Pat. 3,244,650, i.e.

monophenyl di-2-ethyl hexyl phosphite, diphenyl mono-Z-ethyl hexylphosphite, di-isooctyl monotolyl phosphite, tri-Z-ethyl hexyl phosphite,

phenyl dicyclohexyl phosphite, phenyldiethyl phosphite,

triphenyl phosphite,

tricresyl phosphite,

tri(dirnethylphenyl) phosphite, trioctadecyl phosphite,

triisooctyl phosphite,

tridodecyl phosphite,

isooctyl diphenyl phosphite,

diisooctyl phenyl phosphite, tri(t-octylphenyl) phosphite,tri(t-nonylphenyl) phosphite,

benzyl methyl isopropyl phosphite, butyl dicresyl phosphite,

isooctyl di(octylphenyl) phosphite, di(Z-ethylhexyl) (isooctylphenyl)phosphite, tri(2-cyclohexylphenyl) phosphite, tri-alpha-naphthylphosphite, tri(phenylphenyl) phosphite, tri(2-phenylethyl) phosphite,tridodecyl thiophosphite,

tri-p-tert-butyl phenyl thiophosphite, dodecyl thiodiphenyl phosphiteand tert-butyl phenyl thio-di-Z-ethylhexyl phosphite.

The transesterified reaction products of organic polyhydric phenols andorganic phosphite triesters free from phenolic hydroxyl groups may beobtained by heating together the phenol and phosphite ester, preferablyat temperatures of from to 200 C., if necessary under reflux. Toexpedite transesterification it is preferred to add a small amount of analkali or alkaline earth metal oxide, hydroxide or phenolate, in amountof between about .05 to about 1% by weight. Although it is not necessarythat transesterification be complete, it is believed that only thetransesterification product is suitable for use in stabilizing aboutequimolar ethylene/chlorotrifluoroethylene copolymers during meltprocessing in accordance with the present invention because only theyhave sufliciently high boiling points to ensure their presence duringfabrication by melt processing at temperatures of up to about 320 C.Usually, transesterification involving about /3 of the phosphite estergroups of the triphosphite and about /2 of the available phenol groupsof the dihydric phenol on a mol for mol basis, may be sufficient.

The second essential component of the stabilizer system of the presentinvention is a salt of a monocarboxylic acid having from about 6 toabout 24 carbon atoms and a metal of Group II of the Periodic Table. Themetal can, for example, be any one of zinc, calcium, cadmium, barium,magnesium, and strontium. The acid can be any organic monocarboxylicacid having from 6 to about 24 carbon atoms which does not containnitrogen. Suitable acids are also described in US. Pat. 3,244,650. Astherein set forth, the aliphatic, aromatic, alicyclic andoxygencontaining heterocyclic organic acids are operable as a class.Aliphatic acid includes any open chain carboxylic acid, unsubstituted orsubstituted with unreactive groups such as halogens, sulfur or hydroxyl.Alicyclic acid includes any carbocyclic acid having a non-aromatic ringoptionally substituted by an unreactive substituent, such as halogens,hydroxyl groups or alkyl and alkynyl radicals or other carbocyclic ringstructures. Suitable aromatic acids can be carbocyclic oroxygen-containing heterocyclic and may be substituted by an unreactivering substituent such as halogens, alkyl or alkenyl radicals and othersaturated or aromatic rings condensed therewith. Suitable exemplaryorganic acids include those listed in US. Pat. 3,244,650, i.e. hexoicacid, Z-ethylhexoic acid, n-octoic acid, isooctoic acid, capric acid,undecylic acid, lauric acid, myristic acid, palmitic acid, margaricacid, stearic acid, oleic acid, ricinoleic acid, behenic acid,chlorocaproic acid, hydroxy capric acid, benzoic acid, phenylaceticacid, butyl benzoic acid, ethyl benzoic acid, propyl benzoic acid, hexylbenzoic acid, salicyclic acid, naphthoic acid, l-naphthalene aceticacid, orthobenzoyl benzoic acid, naphthenic acids derived frompetroleum, abietic acid, dihydroabietic acid, hexanhydrobenzoic acid,and methyl furoic acid.

Organic zinc salts are preferred for use in the stabilizer compositionsof the present invention, zinc-Z-ethyl hexylate being a specific exampleof a preferred organic zinc salt.

The third essential component of the stabilizing system of the presentinvention, the ester or alkali metal salt of thiodipropionic acid, hasthe general formula:

wherein R and R which may be the same or different, are independentlyselected from the group consisting of hydrogen, alkali metals, straightchain or branched chain alkyl radicals having from 1 to 36 carbon atoms,cycloalkyl radicals having from 3 to 36 carbon atoms, akenyl radicalshaving from 6 to 36 carbon atoms, aryl radicals and alkaryl radicals,with the proviso that not more than one of R and R may be hydrogen. Thealkyl, cycloalkyl, alkenyl, aryl and alkaryl radicals may beunsubstituted or may, if desired, contain unreactive inert substituentssuch as halogens. Exemplary R groups include lithium, sodium, potassium,methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, amyl,isoamyl, n-octyl, isooctyl, 2-ethyl hexyl, t-octyl, decyl, dodecyl,octadecyl, allyl, hexenyl, linoleyl, ricinoleyl, oleyl, phenyl, xylyl,tolyl, ethyl phenyl, naphthyl, cycohexyl, benzyl, cyclopentyl, methylcyclopentyl, ethylcyclohexl, and naphthenyl groups.

Exemplary suitable alkali metal salts and esters of thiodipropionic acidinclude mono and disodium thiodipropionate, mono and dipotassiumthiodipropionate, mixed sodium-potassium thiodipropionate, monolaurylthiodipropionate, dilauryl thiodipropionate, distearyl thiodipropionate,butyl stearyl thiodipropionate, 2-ethylhexyl lauryl thiodipropionate, di2 ethylhexyl thiodipropionate, diisodecyl thiodipropionate, isodecylphenyl thiodipropionate, benzyl lauryl thiodipropionate, benzyl phenylthiodipropionate, the esters of fatty alcohols obtained from tallow,cotton seed oil or soya-bean oil and thiodipropionic acid. These estersas a class are known compounds. Many are commercially available. All canbe prepared by methods known to those skilled in the art involvingesterification of thiodipropionic acid with the corresponding alcohol.

Especially preferred for use in the composition of the present inventionare disodium thiodipropionate, distearyl thiodipropionate, and dilaurylthiodipropionate.

As above stated, the transesterified reaction product of an organicpolyhydric phenol and the organic phosphite triester is employed inamounts within the range of about 0.01 to about 30% by weight of thepolymer. It is preferably employed in amount ranging between about 0.05to about 6% by weight and more preferably yet, 0.1 to about 1% byweight.

Although the salt of the monocarboxylic acid and Group II metal may beemployed in amount of 0.01 to 10% by weight of the polymer, it ispreferred to employ 0.01 to 3%, and, more preferably yet, 0.02 to about0.5%. In most preferred embodiments the weight ratio of thetransesterified reaction product of the organic polyhydric-phenol withthe organic phosphite triester and the Group II metal salt of themonocarboxylic acid ranges between about 4:1 to about 2: 1.

The salt or ester of thiodipropionic acid is usually employed in amountranging between about 0.01 to about 10% by weight of the polymer. It ispreferably employed in amounts between about 0.05 and about 3% byweight, more preferably yet in amounts ranging between about 0.1 andabout 1% by weight of the polymer.

These stabilizers are admixed with the copolymer using conventionalmechanical procedures. The order of addition of the individualcomponents of the stabilizer system has no influence on itseffectiveness. The individual components can be added separately or bemixed prior to addition with equally effective results. Stabilizercomponents can be added in solution or be dry blended with thecopolymer. Liquid or soluble components of the stabilizer system can beadmixed with polar organic solvents containing no hydroxyl groups, suchas ketones and ethers, as well as with non-polar aliphatic or aromaticsolvents, such as hexane, heptane or toluene, and be sprayed onto thepolymer if in finely divided form in conventional tumbling or blendingdevices. For molding operations, such as extrusion or injection molding,the blended mixture may be passed through an extruder and the extrudedrod chopped into pellets of desired size. Alternatively, the stabilizersmay be admixed with the copolymer by tumbling pellets of the copoymer,adding liquid components of the stabilizer system, tumbling again todistribute the liquid portions of the stabilizer, then adding the drycomponents of the stabilizer, continuing tubling to distribute the drycomponents evenly over the surface of the pellets, and then extrudingthe resultant mixture to intimately blend the copolymer and stabilizers.

DESCRIPTION OF PREFERRED EMBODIMENTS Of the following experiments, thoseemploying the three-component stabilizer system of the present inventionillustrate specific preferred embodiments and illustrate the outstandingstabilization achieved by the stabilizing mixtures of the presentinvention.

The thermal stability of stabilized and unstabilizedethylene/chlorotrifluoroethylene copolymers was determined using thefollowing procedures:

(A) Infrared method A one-mil film of the ethylene/chlorotrifiuoroethylene copolymer is prepared by compression molding of copolymerpowder in a Loomis Engineering Press or Carver Press at 260270 C. underloads of 8,000 to 15,000 lbs. The film is mounted on a suitable supportand its infrared spectrum is recorded. The specimen is then thermallyannealed in a forced draft oven in air at 200 C. for specified periodsof time and its infrared spectrum is again recorded. The development ofcarbonyl peaks in the 1,700 cm. region is observed with time ofannealing. Using absorbence at 3,000 cm." as internal standard, ratio ofpeak absorbence at 1,700 emfto peak absorbence in the 3,000 cm.- regionis an indication of degree of oxidation of the copolymer. It was foundthat multiple peaks appear at the frequency range of 1,650 to 1,800 cm.during annealing in air at 200 F. the magnitude of which increases withincreasing annealing time.

To demonstrate its thermal instability, an equimolarethylene/chlorotrifiuoroethy1ene copolymer containing about 50 molpercent of ethylene units and correspondingly about 50 mol percent ofchlorotrifluoroethylene units, having a melting point of 245 C. andcontaining no stabilizers was subjected to thermal stability test usingthe above-described infrared method. Results are shown in Table I below:

TABLE I I. R. absorb ence Absorbence Annealing time in air at 3,000 cm.-1, 700 cmr ratio 200 (3., hrs. (a) (b) (b/c) A plot of annealing timevs. absorbence ratio shows a straight line indicating a fast rate ofthermal oxidation of the copolymer almost immediately upon start ofthermal annealing. Hence, it is clear that the unstabilized copolymerhad no initial stability against thermal degradation.

When the unstabilized copolymer used in the above stability test is meltfabricated by extrusion at 270 C., then the extrudate is discolored,contains voids, and has a rough appearance and, hence, is not suitablefor practical use in any of the applications indicated, supra.

(B) Volumetric method It has been found that thermal degradation ofethylene/ chlorotrifluoroethylene copolymers involves release of acidicgases. To quantitatively determine release of acidic gases upon exposureof the copolymer to elevated temperatures in the presence and absence ofair (in nitrogen) gram portions of the copolymer are introduced into a50 ml. flask equipped with thermometer, an inlet tube for air ornitrogen, and an outlet leading into a known volume of 0.1 N sodiumhydroxide. The flask is immersed in an oil bath maintained at 260 C.,and Carrier gas (air or nitrogen) is introduced at a slow rate into theflask. Ten m1. portions of the 0.1 N sodium hydroxide are withdrawn bypipette at periodic intervals and are titrated with 0.1 N hydrochloricacid using methyl orange as indicator. The decrease in strength of thesodium hydroxide solution, with appropriate correction for volume lossof sodium hydroxide solution, is related to quantity of acidic gasesevolved.

A portion of the unstabilized about equimolarethylene/chlorotrifluoroethylene copolymer used in the above infraredtest was subjected to the volumetric thermal sta-- bility test in air aswell as in nitrogen atmosphere. The results are summarized in Table IIbelow.

TABLE II (a) Air Atmosphere 0.1N HCl titer, ml.

(b) Nitrogen Atmosphere These data, again, indicate that thermaldegradation of the copolymer starts immediately upon exposure toelevated temperaures. They also show clearly that, surprisingly, thermaldecomposition of the copolymer proceeds at a much more rapid pace innitrogen than it does in air.

Various stabilizers known to be efliective for stabilization of ethyleneor chlorotrifluoroethylene homopolyrners were incorporated into anequimolar ethylene/chlorotrifiuoroethylene copolymer containing about 50mol percent of units derived from ethylene having a melting point of 245C. The blends so obtained were subjected to the infrared testabove-described. The results are summarized in Table III, below. In thistable the effective service period is the period of time during whichthe absorbence peak ratio in the 1,700 cmr and 3,000 cmr regionsremained 0, indicating the period of stability against thermaloxidation. Test 8 shown in Table 'III clearly illustrates the superiorperformance of a stabilizer system according to the present invention.The stabilized compositions were prepared by dry blending insolublestabilizer components with the polymer in finely divided form in a ballmill, adding soluble stabilizer components in suitable solvents, mixingthe solution with the polymer, and stripping the solvent.

TABLE III Efleetive serv- Amount ice period, Test I I of stabilhrs. atNo. Stalnhzer izer, phr. 200 C.

1 one 24 2 4,4-thio bis (fi-tert. butyl meta- 0. 3 24 cres '4,4-thiobis(6-tert. butyl meta- 0. 3 3 cresol).

and 27 Distearylthiodipropionate 0. 1 4,4-thio bis(6tert. butyl meta-0.5 4 cresol). 24

and Epoxidized soya bean oil 1. 0 Butylated hydroxytolnene 0.3 5 and 27Distearylthiodipropionate 0. 1 Hydroquinone 0. 25 6 and Zlnc oxide 0.05Chloranil 2 7 and 1 Zinc oxide 0. 2

Phosphite oi 1,1,3-tris (2-methyl-4- 0. 25

hydroxy-5-tert. buty1pheny1)- butane. 8 and 540 Zinc-Z-ethylhexylate- 0.05

an Distearyl thiodipropionate 0. 15

1 Discoloration developed after 24 hrs. at 200 0.

Dry powdered ethylene/chlorotrifluoroethylene copolymer of about 40 meshparticle size containing about 50% of ethylene units having a meltingpoint of 245 C. and a melt index of 0.13 determined according to AST MDl238-65T, was mixed in a ball mill for a period of 1 to 2 hours withvarious amounts of stabilizers in accordance with the present invention.Portions of the resin blend were then charged into a melt rheometer,preheated to 275 C., and after 6 minutes residence time under load themelt index was determined according to ASTM D1238-65T. The load was thenremoved and the molten resin was left in the rheometer for a period 10invention. Portions of the resin blends are then charged into a meltrheometer, as described in ASTM D1238- 65T, maintained at 275 C. andplaced under 12,176 grams load. Cuts of the extrudate were taken at oneminute intervals, and their weights were determined. Re-

of about 15 minutes. Its melt indexwas then redetermmed sults aresummanzed m Table V1 below.

TABLE IV Phosphlte of ,4-nbutylldenebis- Zlne-2- Dlstearyl-(6tert.-butylethylhexthiodipro- Time, Melt Test number m-eresol), phr.ylate, phr. pionate, phr. min 1 Index Appearance at end of test 0. 220.08 0 45 0.10 Discolored, rough.

0 0.3 6 0.13 Charred. 0. 0. 08 0. 1 57 0.12 Clear, smooth. no bubbles.0.075 0.025 0.3 16 0.12 Bubbles, roughness.

0. 22 0.08 0.3 17 0.08 Clear, smooth. 0.075 0.025 0.03 36 0.11 Slightlydiscolored.

4.5 1.5 2. 0 16 0.30 Discolored, rough.

22 8 10.0 16 2.0 Discolored.

Phosphite of 1,1,3-tris( 2- methyM- hydroxy-S-tertbutylphenyl) butane,phr.

0. 22 0.08 0 82 0.10 Clear bubbles. o. 22 0.0a 0.1 16 0.1a Rough,bubbles. 0.075 0.025 0.3 50 0. Discolored.

1 Time elapsed to first observed appearance of visual signs ofdeterioration.

TABLE V Phosphite o1 4,4-n-buty1i- Zinc-2- Dlstearyl- High dene-bis-(G-ethylthiodlproload, tert.butyl-mhexylate, pionate, Time, melt Appearanceat end Test number cresol) phr. phr. phr. min. index of test 0 0 0Charred, blistered. 0. 22 0. 08 0. 1 68 6. 7 Smooth, clear. 0. 22 0.080.3 68 6.8 Some bubbles appeared. 0.22 0.08 0. 04 38 6. 8Bubblesdiscoloration. 0. 22 0.08 0.07 68 6. 8 Smooth, clear. 0. 22 0. 080. 15 68 7. 3 Do.

Phosphite of 1,1,3-tris(2- methyl-4- hydroxy-5- tert.-butylphenyD-butane, phr.

7... 0. 22 0.08 0 38 6. 6 Bubbles-diseoloratlon.

1 Time elapsed to first observed appearance of visual signs 0!deterioration.

until signs of deterioration, i.e. discoloration, roughness, bubbleappearance, or changes in melt index were observed on the extrudates.The results of this test are summarized in Table IV below.

The above tests were repeated as above-described but using the high loadmelt index (21,600 gm. wt.) in the test. The results are summarized inTable V below. The initial high load melt index of the resin was 6.7.

EDry powdered ethylene/chlorotrifluoroethylene copolymer of about 40mesh particle size containing about of ethylene units having a meltingpoint of 245 C. and a melt index of about 2 determined according to ASTMDl238- are mixed in a ball mill for periods of 1 to 2 hours with variousamounts of stabilizers, including stabilizer systems according to thepresent When other phosphites or organic polyhydric phenols, salts ofcarboxylic acids and Group II metals, and thiodipropionic acid esters oralkali metal salts are used to stabilizeethylene/chlorotrifluoroethylene copolymers in accordance with thepresent invention, similar results are obtained, that is to say, theethylene/chlorotrifluoroethylene copolymers resist thermal degradationand are melt processable at temperatures above their meling point and upto about 320 C.

Since various changes and modifications may be made in the inventionwithout departing from the spirit and essential characteristics thereof,it is intended that all matter contained in the above description shallbe interpreted as illustrative only, the invention being limited only bythe scope of the appended claims.

TABLE VI Weight of 1 min. cut of ex- .Amount of trudate, taken afterindistabilizer, cated period [min.], nor- Appearance percent by malizedto g./1O mins. extrudate at Test wt., based longest indicated No.Stabilizer on polymer 5 30 60 90 120 time period Phosphite of1,1,3-tris(2-methyl-4-hydroxy-5-tert.-butlyphenyl)-butene. 0. 22

an Zineg-ethylhexy 0.08 2.2 2.3 1.8 1.8 Clear with bubbles.

an Distearyl thiodipronlnn Mn 0. 1 Phosphite oi4,4-n-buty1idenebis-(6-tert.-butyl-m-cresol) 0. 22

an 11-.-... Zinca2'ethylhexyl 0.08] 1.9 1.9 2.0 1.9 2.0 D0.

an Distearyl thiodlpropionate 0. 1 Phosphite oi 1,1,3-tris(2methyl4-hydroxy-5-tert.-butylphenyl)-butane- 0. 22

an 12..-..-- zincgrethylhexyh 0. 08 1.6 1.7 1.8 1.8 1.8 Do.

an Disodium thiodipropinn n 0. 1 Phosphite oi 4,4-n-butylidenebis-(6-tert.-buty1-m-cresol) 0. 22

an 13 Zineg-ethylhexyl m 0.08 2.3 2.4 1.9 Do.

an Disodium thiodiproninn 0. 1

We claim: phite having the formula (Ra) P wherein a is selected 1. Acopolymer composition having improved thermal stability which comprisesan admixture of an ethylene/ chlorotrifiuoroethylene copolymercontaining about 40 to about 60 mol percent of ethylene units and about40 to about 60 mol percent of chlorotrifiuoroethylene units, and

(a) 0.01 to percent by weight of the polymer of a transesterifiedreaction product obtained from an organic polyhydric phenol selectedfrom the group con sisting of 1,l,3-tri(2-methyl-4-hydroxy-S-tert. butylphenyl) butane and the phenol of the formula M some (Rn h wherein X isselected from the group consisting of oxygen, sulfur, alkylene,alicyclidene, arylidene and mixed alkylene-arylidene andalkylene-alicyclidene groups, wherein the aliphatic or cycloaliphaticportion of the molecule may be straight chain or branched chain, havingfrom 1 to about 18 carbon atoms; wherein the R substituents, which maybe the same or different, are independently selected from the groupconsisting of hydrogen and alkyl, straight or branched chain, havingfrom 1 to about 18 carbon atoms; and wherein mand n are integers from 1to 5, and o and p are integers from 0 to 4, with the proviso that thesums of m+o, and n+p may not not exceed 5, and an organic phosphitetriester free from phenolic hydroxyl groups having up to about 60 carbonatoms obtained by transesterification of the phenol and phosphite at anelevated temperature sufficient to form a homogeneous mixture;

(b) 0.01 to 10 percent by weight of the polymer of a salt of amonocarboxylic acid having from 6 to about 24 carbon atoms and a metalof Group H of the Periodic Table; and

(c) 0.01 to 10 percent by weight of the polymer of an ester or alkalimetal salt of thiodipropionic acid.

2. The composition of claim 1 wherein the copolymer is an aboutequimolar ethylene/chlorotrifluoroethylene copolymer.

3. The composition of claim 1 wherein the transesterified reactionproduct is obtained from an organic phosfrom the group consisting ofoxygen, sulfur and mixtures thereof, and R is selected from the groupconsisting of aryl, alkyl, cycloalkyl, aryl-alkyl and alkyl-aryl.

4. The composition of claim 3 wherein the copolymer is an aboutequimolar ethylene/chlorotrifluoroethylene copolymer.

5. The composition of claim 1 wherein the salt of a monocarboxylic acidis a zinc salt.

6. The composition of claim 3 wherein the salt of a monocarboxylic acidis a zinc salt.

7. The composition of claim 6 wherein the copolymer is an aboutequimolar ethylene/chlorotrifluoroethylene copolymer.

8. The composition of claim 1 wherein the transesterified reactionproduct is a phosphite of 4,4-n-butylidene-bis(6-tert.-butyl-m-cresol)or 1,1,3-tris(2-methyl-4- hydroxy-S -tert.buty1phenyl) butane.

9. The composition of claim 8 wherein the salt of a monocarboxylic acidis a zinc salt.

10. The composition of claim 9 wherein the copolymer is an aboutequimolar ethylene/chlorotrifluoroethylene copolymer.

11. The composition of claim 1 wherein the transesterified reactionproduct is a phosphite of 4,4'-n-butylidene-bis-(6-tert.butyl-m-cresol)or 1,1,3-tris(2-methyl-4- hydroxy-5-tert.-butylphenyl)butane, whereinthe salt of a monocarboxylic acid is zinc-2-ethylhexylate, and whereinthe ester of thiodipropionic acid is distearyl thiodipropionate.

12. The composition of claim 11 wherein the copolymer is an aboutequimolar ethylene/chlorotrifiuoroethylene copolymer.

13. The composition of claim 1 containing 0.05 to 6 percent by weight ofthe polymer of a phosphite of4,4'-nbutylidene-bis(6-tert.butyl-m-cresol) or1,1,3-tris(2-methyl-4-hydroxyl-5-tert.-butylphenyl)butane, 0.01 to 3percent by weight of the polymer of zinc-2-ethylhexylate, and 0.05 to 3percent by weight of the polymer of distearyl dithiodipropionate.

14. The composition of claim 13 wherein the copolymer is an aboutequimolar ethylene/chl0rotriflu0roethylene copolymer.

15. A copolymer composition according to claim 1 containing 0.1 to 1percent by weight of the polymer of phosphite of4,4-n-butylidene-bis-(6-tert.-butyl-m-cresol),

0.02 to 0.5 percent by weight of the polymer of zinc-2- ethylhexylate,and 0.1 to 1 percent by weight of the poly 11161 Of distearyldithiodipropionate.

References Cited UNITED STATES PATENTS 3,245,926 4/ 1966 Parker 260233,281,381 10/ 1966 Hechenbleikner 26023 3,346,536 10/1967 Kauder et a1.26023 14 3,255,136 6/1966 Hacker et a1. 5.--.-- 26023 3,501,446 3/ 1 970Regazzini et a1. "-1- 260--87.5

DONALD E. CZYAIA, Primary Examiner 5 v. P. HOKE, Assistant Examiner us.01. X.R.

26045.7 P, 45.75 R, 45.85 R, 45.85 S, 45.95 C, 45.95 G, 45.95 R

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,745,145 Dated July 10, 1973 Inventor(s) aZi and Alfred It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 2, line 47, "0.01 to 30 by weight" should read 0.01 to 30% byweight Column 2, line 50, Phydroxy" should read --'hydroxyl Column 2,line 56, "melt" should read metal Column 3, line 30, "monomers of"should read monomers at Column 3, line 39, fproducts" should readproduct Column 3, line 41, 'inthe" should read in the i Column 5, line47, "Rioofifigfifi shnilid read iii'OOCCfizCfiz Column 6, line 56,l'tubling" should read ---tumbling Column 7, Table I, under heading"1,700 cm." (10) 6th line i "0.154" Should read 0.153

Column a, Table ii, under ad ng "mm Timeless, Ru (bf; NitrogenAtmosphere", 5th line, "9.60"

should read 87.60 7

Column 10 "line 68, "meling." should read melting Column 11, line 38,"l,1,3--tri" should read 1,1',

Column 12, line 45, "hydroxy-S" should read -"hyd roxylv5 Signed andsealed this -27thdayof November 1973. I. (SEAL) J Attest:

EDWARD M.FLETCHER,JR, RENE D. TEGTMEYER Attesting Officer ActingCommissioner of Patents

